2.
Tom Gehrels
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Anton M. J. Tom Gehrels was a Dutch–American astronomer, Professor of Planetary Sciences, and Astronomer at the University of Arizona, Tucson. Gehrels was born at Haarlemmermeer, the Netherlands on February 21,1925, during World War II he was, as a teenager, active in the Dutch Resistance. After he escaped to England, he was sent back by parachute as an organizer for Special Operations Executive SOE committing sabotage against the German forces, after the war, he attended the University of Leiden where he graduated with a degree in physics and astronomy in 1951. He continued his education at the University of Chicago where he obtained his doctorate in astronomy, in 1960, he moved to the University of Arizona along with Gerard Kuiper where he would remain for the next 50 years. The trio are jointly credited with several thousand discoveries, Gehrels also discovered a number of comets. He was Principal Investigator for the Imaging Photopolarimeter experiment on the Pioneer 10 and Pioneer 11 first flybys of Jupiter and he also initiated the Spacewatch program in 1980 and was its Principal Investigator for electronic surveying to obtain statistics of asteroids and comets, including near-Earth asteroids. Bob McMillan was co-investigator and manager, and became the PI in 1997, Gehrels taught an undergraduate course for non-science majors in Tucson in the Fall, and lectured a brief version of that in the Spring at the Physical Research Laboratory in Ahmedabad, India. His recent research was on universal evolution, which was woven in as the thread through these courses. He was the winner of the 2007 Harold Masursky Award for his outstanding service to planetary science. Gehrels was requested by the Journal Nature to write a review on a book regarding Wernher von Braun and he has therefore charged that von Braun was there regularly and much in charge, and that von Braun bears greater responsibility and guilt than his official biography would imply. Towards the end of the review it reads, Von Braun needs no phony defense. What is needed is a more sophisticated historical perspective, Tom Gehrels was the husband of Aleida J. Gehrels and father of Neil Gehrels, George Gehrels and Jo-Ann Gehrels. The minor planet 1777 Gehrels was named in his honour, the professional and personal papers of Tom Gehrels are held at the University of Arizona. Special airborne services in Europe and Far East, 1944–1948, Astronomy and physics, Leiden University 1951. Ph. D. astronomy and astrophysics, Univ. of Chicago,1956, Professor of Planetary Sciences and Astronomy, Univ. of Arizona, 1961–2011. Binzel, Tom Gehrels, and Mildred Shapely Matthews Tucson, University of Arizona Press ISBN 0-8165-1123-3 Hazards Due to Comets and Asteroids, edited by Tom Gehrels, Mildred Shapley Matthews, and A

3.
Palomar Observatory
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Palomar Observatory is an astronomical observatory located in San Diego County, California, United States,145 kilometers southeast of Los Angeles, California, in the Palomar Mountain Range. It is owned and operated by the California Institute of Technology located in Pasadena, research time is granted to Caltech and its research partners, which include the Jet Propulsion Laboratory and Cornell University. The observatory operates several telescopes, including the famous 200-inch Hale Telescope, astronomer George Ellery Hale, whose vision created the Palomar Observatory, built the worlds largest telescope four times. He published an article in the April 1928 issue of Harpers Magazine called The Possibilities of Large Telescopes, Hale hoped that the American people would understand and support his project. Hale followed this article with a letter to the International Education Board of the Rockefeller Foundation dated April 28,1928, in his letter, Hale stated, No method of advancing science is so productive as the development of new and more powerful instruments and methods of research. The 200-inch telescope is named after astronomer George Hale and it was built by Caltech with a $6 million grant from the Rockefeller Foundation, using a Pyrex blank manufactured by Corning Glass Works. Anderson was the project manager assigned in the early 1940s. The telescope saw first light January 26,1949 targeting NGC2261, the American astronomer Edwin Powell Hubble, perhaps the most important observer of the 20th century, was given the honor of being the first astronomer to use the telescope. Astronomers using the Hale Telescope have discovered distant objects at the edges of the universe called quasars and have given us the first direct evidence of stars in distant galaxies. They have studied the structure and chemistry of intergalactic clouds, leading to an understanding of the synthesis of elements in the universe, porter worked on the designs in collaboration with many engineers and Caltech committee members. The gleaming white building on Palomar Mountain that houses the 200–inch Hale Telescope is considered by many to be The Cathedral of Astronomy, the 200-inch Hale Telescope was first proposed in 1928 and has been operational since 1948. It was the largest telescope in the world for 45 years, a 60-inch reflecting telescope is located in the Oscar Mayer Building. It was dedicated in 1970 to take some of the load off of the Hale Telescope and this telescope was used to discover the first brown dwarf star. The 48-inch Samuel Oschin Telescope was started in 1938 and installed in 1948 and it was initially called the 48–inch Schmidt, and was dedicated to Samuel Oschin in 1986. The dwarf planet Eris was discovered using this instrument, the existence of Eris triggered the discussions in the international astronomy community that led to Pluto being re-classified as a dwarf planet. An 18-inch Schmidt camera became the first operational telescope at the Palomar in 1936, in the 1930s, Fritz Zwicky, a Caltech astronomer, discovered over 100 supernovae in other galaxies with this telescope and gathered the first evidence for dark matter. Comet Shoemaker-Levy 9 was discovered with this instrument in 1993 and it has since been retired and is on display at the small museum/visitor center. The Palomar Testbed Interferometer was an instrument that permitted astronomers to make very high resolution measurements of the sizes

4.
Philoctetes
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Philoctetes, or Philocthetes, according to Greek mythology, was the son of King Poeas of Meliboea in Thessaly. He was a Greek hero, famed as an archer, Philoctetes was the subject of four different plays of ancient Greece, each written by one of the three major Greek tragedians. Of the four plays, Sophocles Philoctetes is the one that has survived. Sophocles Philoctetes at Troy, Aeschylus Philoctetes and Euripides Philoctetes have all been lost, Philoctetes is also mentioned in Homers Iliad, Book 2, which describes his exile on the island of Lemnos, his being wounded by snake-bite, and his eventual recall by the Greeks. The recall of Philoctetes is told in the lost epic Little Iliad, Philoctetes killed three men at Troy. Philoctetes was the son of King Poeas of the city of Meliboea in Thessaly, Heracles wore the shirt of Nessus and built his own funeral pyre. No one would light it for him except for Philoctetes, or in other versions his father Poeas and this gained him the favor of the newly deified Heracles. Because of this, Philoctetes or Poeas was given Heracles bow, Philoctetes was one of the many eligible Greeks who competed for the hand of Helen, the Spartan princess, according to legend, she was the most beautiful woman in the world. As such, he was required to participate in the conflict to reclaim her for Menelaus in the Trojan War, Philoctetes was stranded on the island of Lemnos by the Greeks on the way to Troy. There are at least four separate tales about what happened to strand Philoctetes on his journey to Troy, One version holds that Philoctetes was bitten by a snake that Hera sent to molest him as punishment for his or his fathers service to Heracles. Another tradition says that the Greeks forced Philoctetes to show them where Heracless ashes were deposited, Philoctetes would not break his oath by speech, so he went to the spot and placed his foot upon the site. Immediately, he was injured in the foot that touched the soil over the ashes, when, in expiation, the Achaeans offered a sacrifice to Apollo, a snake came out from the altar and bit Philoctetes. Finally, it is said that Philoctetes received his wound on the island of Chryse. A modern interpretation of the cause of his wound is that he was scratched by a poisoned arrow, commonly tips of arrows were poisoned with a combination of fermented viper venom, blood or plasma, and feces. Even a scratch would result in death, sometimes drawn out, a person who survives would do so with a festering wound. Regardless of the cause of the wound, Philoctetes was exiled by the Greeks and was angry at the treatment he received from Odysseus, King of Ithaca, medôn took control of Philoctetes men, and Philoctetes himself remained on Lemnos, alone, for ten years. Helenus, the son of King Priam of Troy, was forced to reveal, under torture. Upon hearing this, Odysseus and a group of men rushed back to Lemnos to recover Heracles weapons, surprised to find the archer alive, the Greeks balked on what to do next

5.
Minor planet
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A minor planet is an astronomical object in direct orbit around the Sun that is neither a planet nor exclusively classified as a comet. Minor planets can be dwarf planets, asteroids, trojans, centaurs, Kuiper belt objects, as of 2016, the orbits of 709,706 minor planets were archived at the Minor Planet Center,469,275 of which had received permanent numbers. The first minor planet to be discovered was Ceres in 1801, the term minor planet has been used since the 19th century to describe these objects. The term planetoid has also used, especially for larger objects such as those the International Astronomical Union has called dwarf planets since 2006. Historically, the asteroid, minor planet, and planetoid have been more or less synonymous. This terminology has become complicated by the discovery of numerous minor planets beyond the orbit of Jupiter. A Minor planet seen releasing gas may be classified as a comet. Before 2006, the IAU had officially used the term minor planet, during its 2006 meeting, the IAU reclassified minor planets and comets into dwarf planets and small Solar System bodies. Objects are called dwarf planets if their self-gravity is sufficient to achieve hydrostatic equilibrium, all other minor planets and comets are called small Solar System bodies. The IAU stated that the minor planet may still be used. However, for purposes of numbering and naming, the distinction between minor planet and comet is still used. Hundreds of thousands of planets have been discovered within the Solar System. The Minor Planet Center has documented over 167 million observations and 729,626 minor planets, of these,20,570 have official names. As of March 2017, the lowest-numbered unnamed minor planet is 1974 FV1, as of March 2017, the highest-numbered named minor planet is 458063 Gustavomuler. There are various broad minor-planet populations, Asteroids, traditionally, most have been bodies in the inner Solar System. Near-Earth asteroids, those whose orbits take them inside the orbit of Mars. Further subclassification of these, based on distance, is used, Apohele asteroids orbit inside of Earths perihelion distance. Aten asteroids, those that have semi-major axes of less than Earths, Apollo asteroids are those asteroids with a semimajor axis greater than Earths, while having a perihelion distance of 1.017 AU or less. Like Aten asteroids, Apollo asteroids are Earth-crossers, amor asteroids are those near-Earth asteroids that approach the orbit of Earth from beyond, but do not cross it

6.
Jupiter trojan
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The Jupiter trojans, commonly called Trojan asteroids or just Trojans, are a large group of asteroids that share the orbit of the planet Jupiter around the Sun. Relative to Jupiter, each Trojan librates around one of Jupiters two stable Lagrangian points, L4, lying 60° ahead of the planet in its orbit, and L5, 60° behind. Jupiter trojans are distributed in two elongated, curved regions around these Lagrangian points with an average axis of about 5.2 AU. The first Jupiter trojan discovered,588 Achilles, was spotted in 1906 by German astronomer Max Wolf, a total of 6,178 Jupiter trojans have been found as of January 2015. By convention they are named after a mythological figure from the Trojan War. The total number of Jupiter trojans larger than 1 km in diameter is believed to be about 1 million, like main-belt asteroids, Jupiter trojans form families. Jupiter trojans are bodies with reddish, featureless spectra. The Jupiter trojans densities vary from 0.8 to 2.5 g·cm−3, Jupiter trojans are thought to have been captured into their orbits during the early stages of the Solar Systems formation or slightly later, during the migration of giant planets. NASA has announced the discovery of an Earth trojan, the trapped body will librate slowly around the point of equilibrium in a tadpole or horseshoe orbit. These leading and trailing points are called the L4 and L5 Lagrange points, however, no asteroids trapped in Lagrange points were observed until more than a century after Lagranges hypothesis. Those associated with Jupiter were the first to be discovered, E. E. Barnard made the first recorded observation of a Trojan,1999 RM11, in 1904, but neither he nor others appreciated its significance at the time. Barnard believed he saw the recently discovered Saturnian satellite Phoebe, which was only two away in the sky at the time, or possibly an asteroid. The objects identity was not realized until its orbit was calculated in 1999, in 1906–1907 two more Jupiter trojans were found by fellow German astronomer August Kopff. Hektor, like Achilles, belonged to the L4 swarm, whereas Patroclus was the first asteroid known to reside at the L5 Lagrangian point, by 1938,11 Jupiter trojans had been detected. This number increased to 14 only in 1961, as instruments improved, the rate of discovery grew rapidly, by January 2000, a total of 257 had been discovered, by May 2003, the number had grown to 1,600. Asteroids in the L4 group are named after Greek heroes, confusingly,617 Patroclus was named before the Greece/Troy rule was devised, and a Greek name thus appears in the Trojan node. The Greek node also has one misplaced asteroid,624 Hektor, estimates of the total number of Jupiter trojans are based on deep surveys of limited areas of the sky. The L4 swarm is believed to hold between 160–240,000 asteroids with diameters larger than 2 km and about 600,000 with diameters larger than 1 km

The ecliptic is the circular path on the celestial sphere that the Sun appears to follow over the course of a year; it …

The plane of Earth's orbit projected in all directions forms the reference plane known as the ecliptic. Here, it is shown projected outward (gray) to the celestial sphere, along with Earth's equator and polar axis (green). The plane of the ecliptic intersects the celestial sphere along a great circle (black), the same circle on which the Sun seems to move as Earth orbits it. The intersections of the ecliptic and the equator on the celestial sphere are the vernal and autumnal equinoxes (red), where the Sun seems to cross the celestial equator.

The astronomical unit (symbol: au or ua) is a unit of length, roughly the distance from Earth to the Sun. However, that …

The red line indicates the Earth–Sun distance, which on average is about 1 astronomical unit.

Transits of Venus across the face of the Sun were, for a long time, the best method of measuring the astronomical unit, despite the difficulties (here, the so-called "black drop effect") and the rarity of observations.

The astronomical unit is used as the baseline of the triangle to measure stellar parallaxes (distances in the image are not to scale).

In celestial mechanics, the mean anomaly is an angle used in calculating the position of a body in an elliptical orbit …

Area swept out per unit time by an object in an elliptical orbit (grey) and by an imaginary object in a circular orbit (red) which completes its orbit in the same period of time. Both sweep out equal areas in equal times, but the angular rate of sweep varies for the elliptical orbit and is constant for the circular orbit. Shown are mean anomaly and true anomaly for two units of time.